diff --git a/src/Eccube/Controller/Admin/Content/FileController.php b/src/Eccube/Controller/Admin/Content/FileController.php
index 228a825546c..cb5713a2bf1 100644
--- a/src/Eccube/Controller/Admin/Content/FileController.php
+++ b/src/Eccube/Controller/Admin/Content/FileController.php
@@ -37,7 +37,7 @@ class FileController extends AbstractController
     public const SJIS = 'sjis-win';
     public const UTF = 'UTF-8';
     private $errors = [];
-    private $encode = '';
+    private $encode;
 
     /**
      * FileController constructor.
diff --git a/src/Eccube/Doctrine/Query/JoinClause.php b/src/Eccube/Doctrine/Query/JoinClause.php
index f8eb1adf0a2..9e3fb29f214 100644
--- a/src/Eccube/Doctrine/Query/JoinClause.php
+++ b/src/Eccube/Doctrine/Query/JoinClause.php
@@ -30,7 +30,7 @@ class JoinClause
 
     private $indexBy;
 
-    private $leftJoin = false;
+    private $leftJoin;
 
     /**
      * @var JoinClauseWhereCustomizer
@@ -52,7 +52,7 @@ class JoinClause
      * @param $condition
      * @param $indexBy
      */
-    private function __construct($leftJoin, $join, $alias, $conditionType = null, $condition = null, $indexBy = null)
+    private function __construct(bool $leftJoin, $join, $alias, $conditionType = null, $condition = null, $indexBy = null)
     {
         $this->leftJoin = $leftJoin;
         $this->join = $join;
@@ -77,7 +77,7 @@ private function __construct($leftJoin, $join, $alias, $conditionType = null, $c
      *
      * @return JoinClause
      */
-    public static function innerJoin($join, $alias, $conditionType = null, $condition = null, $indexBy = null)
+    public static function innerJoin($join, $alias, $conditionType = null, $condition = null, $indexBy = null): JoinClause
     {
         return new JoinClause(false, $join, $alias, $conditionType, $condition, $indexBy);
     }
@@ -95,7 +95,7 @@ public static function innerJoin($join, $alias, $conditionType = null, $conditio
      *
      * @return JoinClause
      */
-    public static function leftJoin($join, $alias, $conditionType = null, $condition = null, $indexBy = null)
+    public static function leftJoin($join, $alias, $conditionType = null, $condition = null, $indexBy = null): JoinClause
     {
         return new JoinClause(true, $join, $alias, $conditionType, $condition, $indexBy);
     }
@@ -107,7 +107,7 @@ public static function leftJoin($join, $alias, $conditionType = null, $condition
      *
      * @return $this
      */
-    public function addWhere(WhereClause $whereClause)
+    public function addWhere(WhereClause $whereClause): self
     {
         $this->whereCustomizer->add($whereClause);
 
@@ -121,7 +121,7 @@ public function addWhere(WhereClause $whereClause)
      *
      * @return $this
      */
-    public function addOrderBy(OrderByClause $orderByClause)
+    public function addOrderBy(OrderByClause $orderByClause): self
     {
         $this->orderByCustomizer->add($orderByClause);
 
@@ -147,7 +147,7 @@ class JoinClauseWhereCustomizer extends WhereCustomizer
      */
     private $whereClauses = [];
 
-    public function add(WhereClause $whereClause)
+    public function add(WhereClause $whereClause): void
     {
         $this->whereClauses[] = $whereClause;
     }
@@ -158,7 +158,7 @@ public function add(WhereClause $whereClause)
      *
      * @return WhereClause[]
      */
-    protected function createStatements($params, $queryKey)
+    protected function createStatements($params, $queryKey): array
     {
         return $this->whereClauses;
     }
@@ -168,7 +168,7 @@ protected function createStatements($params, $queryKey)
      *
      * @return string
      */
-    public function getQueryKey()
+    public function getQueryKey(): string
     {
         return '';
     }
@@ -192,7 +192,7 @@ public function add(OrderByClause $orderByClause)
      *
      * @return OrderByClause[]
      */
-    protected function createStatements($params, $queryKey)
+    protected function createStatements($params, $queryKey): array
     {
         return $this->orderByClauses;
     }
@@ -202,7 +202,7 @@ protected function createStatements($params, $queryKey)
      *
      * @return string
      */
-    public function getQueryKey()
+    public function getQueryKey(): string
     {
         return '';
     }
diff --git a/src/Eccube/Service/PurchaseFlow/InvalidItemException.php b/src/Eccube/Service/PurchaseFlow/InvalidItemException.php
index f6f011670b6..48f2b677e7e 100644
--- a/src/Eccube/Service/PurchaseFlow/InvalidItemException.php
+++ b/src/Eccube/Service/PurchaseFlow/InvalidItemException.php
@@ -17,7 +17,7 @@
 
 class InvalidItemException extends \Exception
 {
-    private $messageArgs = [];
+    private $messageArgs;
 
     private $warning;
 
@@ -31,7 +31,7 @@ public function __construct($message = null, $messageArgs = [], $warning = false
     /**
      * @return array
      */
-    public function getMessageArgs()
+    public function getMessageArgs(): array
     {
         return $this->messageArgs;
     }
@@ -39,7 +39,7 @@ public function getMessageArgs()
     /**
      * @return bool
      */
-    public function isWarning()
+    public function isWarning(): bool
     {
         return $this->warning;
     }
@@ -47,7 +47,7 @@ public function isWarning()
     /**
      * @return InvalidItemException
      */
-    public static function fromProductClass($errorMessage, ProductClass $ProductClass)
+    public static function fromProductClass($errorMessage, ProductClass $ProductClass): self
     {
         $productName = $ProductClass->getProduct()->getName();
         if ($ProductClass->hasClassCategory1()) {